Fluid pressure operated actuators with piston position sensors are, generally speaking, known in the art, for example, see U.S. Pat. Nos. 4,656,457; 4,523,514; 3,726,191; 3,141,381; and Reissue No. 25,257. Fluid operated actuators find widespread use in machine and other manufacturing equipment. The actuators, typically of the compressed air or hydraulic operated type, use axial movement of a piston within a housing to effect a desired action of a working component attached to the external end of a piston rod connected to the piston. Control valves operated by sensors, such as limit switches, are employed to control the actuators by causing the desired directional movement of the piston at the correct time in the machine sequence.
Since it is often necessary to know when the piston has moved to the fully extended or retracted travel position before the next step in the machine sequence can take place, limit switches have been used to contact the external end of the piston rod or the connected work component at the end of piston travel. However, the use of such externally mounted limit switches encounter several problems since such switches are susceptible to damage in the crowded mechanical environment in which they are located. Furthermore, externally mounted limit switches are bulky and require special mounting arrangements which must be added to the machine.
To overcome these problems, sensors or limit switches have been mounted directly on fluid operated actuators and sense the position of the piston within the housing. For example, see U.S. Pat. No. 4,632,018 and U.S. Pat. No. 4,316,145. The sensors are contained within the housing mounted directly on the actuator, typically by fasteners, such as screws or bolts, and extend through a bore formed in the housing into proximity with the piston or piston rod.
While the use of sensors mounted directly on the housing eliminate many of the problems associated with externally positioned limit switches, they are not without their own disadvantages. Since such sensors are mounted in a single fixed position on the cylinder, the wiring or other connections to remotely located control equipment exit the housing from only one direction or side. This places considerable restraints on the machine designer in mounting a fluid operated cylinder on a machine since they must provide space for such connections in the oftentimes crowded machine environment.
Thus, it would be desirable to provide a fluid operated cylinder position sensor mounting apparatus which overcomes the problems associated with previously devised position sensor mounting apparatuses. It would also be desirable to provide a position sensor mounting apparatus for fluid operated cylinders which permits wiring or other connections leaving the sensor housing to be located in any desired orientation. Finally, it would be desirable to provide a position sensor mounting apparatus for fluid operated cylinders which can be located in any position or angular orientation on the cylinder without requiring removal and reattachment of the sensor on the cylinder.